Stage Distribution of Breast Cancer Diagnosed Before and After Implementation of Population-Based Mammographic Screening

Abstract

Purpose: The German mammographic screening program is very similar to the Norwegian Breast Cancer Screening Program (NBCSP), which started about 10 years earlier. This study analyzes the stage distribution of invasive breast cancers diagnosed in the pre-screening and screening period, and evaluates the overall mortality in women aged 55 – 74 in the pilot and non-pilot counties of the NBCSP.

Materials and Methods: The NBCSP invites women aged 50 – 69 to participate in two-view mammography biennially. Chi-square statistics were used to compare percentages of the stage and treatment of invasive breast cancers diagnosed in women residing in the four pilot counties in the pre-screening (1984 – 1995) and screening (1996 – 2007) period. An ecological approach was used to analyze the age-specific mortality in the pilot and non-pilot counties for the period 1970 – 2007.

Results: 50 % of the breast cancers diagnosed in the pre-screening period, 70 % of the cases detected with screening, 43 % of the interval cancers, and 52 % of the cancers diagnosed outside the NBCSP were stage I. Stage III + was present in 11 % of the cancers in the pre-screening period, and in 1 % of the cancers detected with screening. In the screening period, the breast cancer mortality rate decreased substantially more in the pilot counties than in the non-pilot counties.

Conclusion: The stage distribution of breast cancer diagnosed in the NBCSP is prognostically favorable compared to cancers diagnosed outside the screening program. The reduction in the breast cancer mortality rate was more pronounced in the four pilot counties compared to the non-pilot counties. It is necessary to evaluate the program based on individual data.

Zusammenfassung

Ziel: Das Mammografie-Screening-Programm in Deutschland ist dem Norwegischen Brust-Cancer-Screening-Programm (NBCSP), das ungefähr 10 Jahre früher angefangen hat, sehr ähnlich. Das Ziel unserer Studie ist die Analyse der Stadieneinteilung von invasivem Brustkrebs diagnostiziert vor und nach Einführung des Screenings sowie die Evaluation der Mortalität von Frauen in der Altersgruppe 55 – 74 Jahren in den Pilot- und Nicht-Pilot-Ländern des NBCSP.

Material und Methoden: Im NBCSP werden alle Frauen im Alter 50 – 69 Jahren zu einer 2-Ebenen-Mammografie jedes 2. Jahr eingeladen. Die Chi-Square-Statistik wurde zum Vergleich von prozentualem Anteil von Stadien und Behandlung von invasivem Brustkrebs in den 4 Pilot-Ländern in der Pre-Screening- (1984 – 1995) und der Screening- (1996 – 2007) Periode verwendet. Eine ökologische Evaluation wurde verwendet, um die altersspezifischen Mortalitätsraten in den Pilot- und Nicht-Pilot-Ländern für die Periode 1970 – 2007 zu analysieren.

Ergebnisse: Stadium I kam unter den invasiven Karzinomen in 50 % in der Pre-Screening-Periode, in 70 % unter den Screening-detektierten Karzinomen, in 43 % unter den Intervallkarzinomen und in 52 % unter den Karzinomen außerhalb des NBCSP vor. Fast 11 % der Karzinome in der Pre-screening-Periode waren Stadium III + verglichen mit 1 % für Screening-detektierte Karzinome. In der Screening-Periode hat die Mortalität an Brustkrebs in den Pilot-Ländern verglichen mit den Nicht-Screening-Ländern wesentlich mehr abgenommen.

Schlussfolgerung: Die Stadien-Einteilungen des im NBCSP diagnostizierten Brustkrebses sind prognostisch wesentlich günstiger als die Karzinome, die außerhalb des Programms gefunden werden. Die reduzierte Mortalität von Brustkrebs war deutlicher in den 4 Pilot-Ländern verglichen mit den Nicht-Pilot-Ländern. Es besteht die Notwendigkeit einer Evaluation des NBCSP aufgrund von individuellen Daten.

Key words

breast - mammography - screening

• References

• 1 Perry N, Broeders M, deWolf C et al. European guidelines for quality assurance in breast cancer screening and diagnosis. 4th ed. European Communities. Luxemburg: Office for Official Publications of the European Communities; 2006. ISBN: 92-79-01258-4 http://bookshop.eu.int
• 2 Vainio H, Bianchini F (eds) IARC Handbook of Cancer Prevention. Volume 7: Breast Cancer Screening. France, Lyon: IARCPress; 2002 http://www.iarc.fr
• 3 Tabár L, Vitak B, Chen HH et al. The Swedish Two-County Trial twenty years later. Updated mortality results and new insights from long-term follow-up. Radiol Clin North Am 2000; 38: 625-651
• 4 Nystrom L, Andersson I, Bjurstam N et al. Long-term effects of mammography screening: updated overview of the Swedish randomised trials. Lancet 2002; 359: 909-919
• 5 Moss SM, Cuckle H, Evans A et al. Effect of mammographic screening from age 40 years on breast cancer mortality at 10 years’ follow-up: a randomised controlled trial. Lancet 2006; 368: 2053-2060
• 6 Tabar L, Yen MF, Vitak B et al. Mammography service screening and mortality in breast cancer patients: 20-year follow-up before and after introduction of screening. Lancet 2003; 361: 1405-1410
• 7 Paap E, Holland R, den Heeten GJ et al. A remarkable reduction of breast cancer deaths in screened versus unscreened women: a case-referent study. Cancer Causes Control 2010; 21: 1569-1573
• 8 Swedish Organised Service Screening Evaluation Group. Reduction in breast cancer mortality from organized service screening with mammography: 1. Further confirmation with extended data. Cancer Epidemiol Biomarkers Prev 2006; 15: 45-51
• 9 Olsen AH, Njor SH, Vejborg I et al. Breast cancer mortality in Copenhagen after introduction of mammography screening: cohort study. BMJ 2005; 330: 220-225
• 10 Larsen IK, Smastuen M, Johannesen TB et al. Data quality at the Cancer Registry of Norway: an overview of comparability, completeness, validity and timeliness. Eur J Cancer 2009; 45: 1218-1231
• 11 Regulations on the collection and processing of personal health data in the Cancer Registry of Norway (Cancer Registry Regulations). http://www.lovdata.no
• 12 Hofvind S, Geller B, Vacek PM et al. Using the European guidelines to evaluate the Norwegian Breast Cancer Screening Program. Eur J Epidemiol 2007; 22: 447-455
• 13 Cancer Registry of Norway. Cancer statistics. http://kreftregisteret.no/no/Registrene/Kreftstatistikk
• 14 Hofvind S, Sakshaug S, Ursin G et al. Breast cancer incidence trends in Norway – explained by hormone therapy or mammographic screening?. Int J Cancer 2011; (in press)
• 15 Lambe M, Wigertz A, Holmqvist M et al. Reductions in use of hormone replacement therapy: effects on Swedish breast cancer incidence trends only seen after several years. Breast Cancer Res Treat 2010; 121: 679-683
• 16 Skaane P. Studies comparing screen-film mammography and full-field digital mammography in breast cancer screening: updated review. Acta Radiol 2009; 50: 3-14
• 17 Jacobsen GD, Jacobsen KH. Health awareness campaigns and diagnosis rates: evidence from National Breast Cancer Awareness Month. J Health Econ 2011; 30: 55-61
• 18 Zahl PH, Gøtzsche PC, Mæhlen J. Natural history of breast cancers detected in the Swedish mammography screening programme: a cohort study. Lancet Oncol 2010; 12: 1118-1124
• 19 Jørgensen KJ, Zahl PH, Gøtzsche PC. Overdiagnosis in organised mammography screening in Denmark. A comparative study. BMC Womens Health 2009; 22: 36
• 20 Puliti D, Miccinesi G, Paci E. Overdiagnosis in breast cancer: design and methods of estimation in observational studies. Prev Med 2011; 53: 131-133
• 21 Ernster VL, Ballard-Barbash R, Barlow WE et al. Detection of ductal carcinoma in situ in women undergoing screening mammography. J Natl Cancer Inst 2002; 16: 1546-1554
• 22 Sørum R, Hofvind S, Skaane P et al. Trends in incidence of ductal carcinoma in situ: the effect of a population-based screening programme. Breast 2010; 19: 499-505
• 23 Duffy SW, Agbaje O, Tabar L et al. Overdiagnosis and overtreatment of breast cancer: estimates of overdiagnosis from two trials of mammographic screening for breast cancer. Breast Cancer Res 2005; 7: 258-265
• 24 Lynge E, Braaten T, Njor SH et al. Mammography activity in Norway 1983 to 2008. Acta Oncol 2011; 50: 1062-1067
• 25 Holleczek B, Arndt V, Stegmaier C et al. Trends in breast cancer survival in Germany from 1976 to 2008-A period analysis by age and stage. Cancer Epidemiol 2011; 35: 399-406
• 26 Kalager M, Zelen M, Langmark F et al. Effect of screening mammography on breast-cancer mortality in Norway. N Engl J Med 2010; 363: 1203-1210
• 27 Skaane P. Nationwide mammography screening registers: the best way to go for mortality evaluation – but there is no free lunch. Acta Radiol 2011; 52: 235
• 28 van Ravesteyn NT, Heijnsdijk EA, de Koning HJ. More on screening mammography. N Engl J Med 2011; 364: 282-283
• 29 Duffy SW, Smith RA. More on screening mammography. N Engl J Med 2011; 364: 283-286
• 30 Green BB, Taplin SH. Breast cancer screening controversies. J Am Board Fam Pract 2003; 16: 233-241
• 31 Olsen AH, Njor SH, Lynge E. Estimating the benefits of mammography screening: the impact of study design. Epidemiology 2007; 18: 487-492
• 32 Holmberg L, Duffy SW, Yen AM et al. Differences in endpoints between the Swedish W-E (two county) trial of mammographic screening and the Swedish overview: methodological consequences. J Med Screen 2009; 16: 73-80
• 33 Gøtzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database Syst Rev 2011; CD001877 . Review